Short wave communication system



April 1941. u. E. LBENDENBLAD- 2,233,904

SHORT WAVE COMMUNICATION SYSTEM Original Filed April 28, 1936 3Sheets-Sheet-i 22 Z5 Y4 I l 2 I L 4 #1 L 4 r L 4 1 I 4 2 v l 2 2. 7 1? r4 IJ H mix 20 Afz/ dvz {H 23 i 1% z INVENTOR. mggmsfifigmgpwgg L By msE. L/NDENBLAD RECEIVER- 55/5 5 H ATTORNEY.

April 1 N. E. LINDENBLAD 2,238,904

SHORT WAVE COMMUNICATION SYSTEM Original Filed April 28. 1936 3Sheets-Sheet 2 ROOF INVEN TOR.

Mi? L/NDENBLAD A TTORNEY.

April 22, 1941. N. E. LINbENBLAD 2,2 ,9 4

SHORT WAVE COMMUNICATION SYSTEM Original Filed April 28, 1936 3Sheets-Sheet 3 TOA/VTENA /A (Fla. 2)

I v 46 53 *1 I E v m VIDEO mm/s. L

AIM

70 VOICE n m/ws (/22) INVEN TOR.

P & 5. LINDENBLAD BY ATTORNEY,

Patented Apr. 22, 1941 2.238.904 snon'r WAVE COMMUNICATION SYSTEM NilsE. Lindenblad, Port Jefferson, N. Y., assignor to Radio Corporation ofAmerica, a corporation of Delaware Original application April 28, 1936,Serial No. 76,745. Divided and this application January 6, 1938, SerialNo. 183,571

26 Claims. ((31. 178-44) This invention is a division of United StatesPatent; No. 2,131,108, granted September 2'7, 1938, on an applicationSerial No. 76,745 filed April 28, 1936, and relates to transmission linesystems and feeders for high frequency loads, such as antenna systems.

Some of the objects of the invention are; to provide a rigid andpractical ultra high frequency antenna structure for use on the tops ofhigh buildings wherein the feeders themselves form supports for theradiating elements; to match the surge impedances of the radiatingelements to the impedances of the supporting feeders; to obtain animpedance match between a plurality of branch feeders and a main feederwithout introducing excessive circulating energy in the system; toprovide an impedance matching device in the form of a concentrictransmission line; to enable the connection and impedance matching of asingle concentric conductor system to a plurality of concentricconductor systems; and to couple a concentric transmission line to apair of conductors adapted to have oppositely flowing currents thereonwith means for pre venting the flow of current on the exterior of theouter conductor of the concentric line.

The invention includes among its features:

(1) An antenna system formed of a plurality of units in differentparallel planes, each unit of which comprises an equilateral triangularaffair having a plurality of half wavelength conductors which areangularly disposed at substantially 60 with respect to one another, theconcluctors in one unit being fed at points intermediate the ends whilethe conductors in a parallel plane are fed from the ends.

(2) A feeder in the form of a concentric line having inner and outerconductors whose relative diametrical dimensions vary to produce desiredchanges in impedance of the feeder.

like reference numerals indicate like parts throughout the figures.

Fig. 1 illustrates an antenna embodiment of the invention employingaerial elements which form sides of one or more equilateral triangles,and wherein the aerial elements are fed from the supporting rods;

Figs. 1a and 1b are given for the purpose of exposition and show thecurrent distribution pat tern in the aerial elements of adjacenttriangular units;

Fig. 1c is a view showing the system of Fig. l unfolded in a singleplane in order to more completely illustrate the structure of Fig. 1 andthe manner in which the various elements thereof are energized;

Fig. 2 illustrates a preferred embodiment of antenna, impedance matchingsystem, and feeder system in accordance with the invention;

Fig. 3 is a detail of the system of Fig. 2 showing one pair ofsupporting feeders and associated apparatus in order to more clearlyillustrate the principles of the invention;

Fig. 4 discloses an alternative arrangement to that of Fig. 3 forfeeding the doublets of the difierent triangular units; and

Fig. 5 illustrates a circuit arrangement of filter and impedance circuitwhich may be employed in feeding energy from a plurality of transmittersto an antenna system of the type shown in Fig.2.

Fig. 1 shows one satisfactory antenna embodiment for achieving widefrequency band communication. Here there are provided six transmissionlines comprising three pairs of vertical (3) An arrangement for feedingan antenna connects with a two-wire transmission line TL extending tohigh frequency apparatus through antenna tuning and impedance matchingdevice 4 (note Fig. 1c). These three pairs of feeders form a six wirecage in which adjacent feeders are of opposite phase. Such a cagearrangement of feeders is known to give very little radiation even whenthe spacing is an appreciable fraction of a wavelength, for example, aneighth of a wavelength. The fact that these feeders can be separatedwithout producing radiation is utilized in making the cage serve as asupport for the triangular radiating units N, O and P. Each unitcomprises three half-wavelength doublets forming sides of an open equilateral triangle. Unit P contains doublets 24, 25 and 26; unit 0contains doublets 21, 28 and 29; and unit N contains doublets 30, 3| and32. The feeders l8, I9, 20, etc., are in the form of rigid pipes onwhich the individual doublets of the equilateral triangular units may bemounted directly, or, as shown in the drawing for mechanical andelectrical reasons, supported through metallic brackets 25'. Allbrackets 25' are of the same length and the impedance of these includingthe vertical feeders are matched to the impedance of the doublets atspaced points on the doublets intermediate the ends thereof in wellknown manner. In other words, each doublet is arranged to introduce aload which matches the vertical feeders at the points of connection sothat a minimum or no standing wave is set up on the vertical feeders.Since the phase lag introduced by the additional length of brackets 25is the same in all triangular units N, O and P,

they do not affect the phase relations between the triangular units. Theunits are here shown spaced one-half wavelength apart, correspondinglylocated doublets of which are located one wavelength apart. Sinceadjacent equilateral triangular units are one-half wavelength apart, thesame feeder will have opposite polarities at the points of connection sospaced, for which reason it is necessary to reverse the order ofpolarity connection of the individual doublets of the adiacenttriangular units so that the currents in adjacent triangles may have thesame direction, This current direction is illustrated in Figs. 1a and 1bas being counterclockwise, although it will be appreciated that thedirection of the currents in all the equilateral triangular units N. Oand P may be reversed. Figs. 1a and 1b are plan views of the triangularunits P and 0, respectively, and indicate how the individual doublets ofeach unit on each level are fed from different feeder wires. It will beobserved, among other things, that the doublets of adjacent triangularunits, such as P and O, are differently positioned, while those ofalternately located units, such as P and N, are similarly positioned.Referring to Fig. 1a as an example, it will be seen that feeders I8 and23 feed doublet 24 of unit P, whereas in the adjacent lower unit 0,(note Fig. 1b) these two feeders help feed two different doublets. Themanner of feeding all doublets of the triangular units N, O and P willbe more clearly understood from an inspection of Fig. 10, which is anunfolded view of the antenna structure as it would look if the feedersand doublets were all placed in a single plane.

When feeding the system of Fig. 1, as shown in Fig. 10, it may bedesirable to change the dimensions of the feeders l8, I9, 28, etc.,abruptly at successive levels at which they connect with the theirlengths, since this would call for large changes in diameter of thefeeders. A slight mismatch of the feeders, especially if the voltagenodal points of the thus created standing wave portion of the totalenergy on the feeder (since some standing waves are created with amismatch) are located mid-way between adjacent,

triangular units, is not, however, detrimental to the system, since inthis condition the polarities at the terminals of each half wave sectionbetween adjacent triangular units is reversed and of equal amplitude,regardless of whether there is a standing or traveling wave in thesection.

If new we consider a case where the maximum point of a standing voltagewave on the feeders instead of a minimum falls midway between adjacenttriangular radiating units, we may have a very different mode of tuninif at the same time the impedance offered by the individual doubletsacross the feeders is inductive. The case then is similar to thesituation described in my United States Patent No. 1,821,385, grantedSeptember 1, 1931, wherein there is obtained an infinite phase velocityalong the feeders so that all points along each feeder is at the samephase. In this particular case the adjacent triangular units do not needto have the order of connection of the individual radiating doubletschanged as shown in Figs. 1 to lo, and instead all triangular units mayhave their correspondingly located doublets similarly located along thefeeder line. Because of this phase phenomenon, there is no need toemploy any particular spacing between adjacent units. It is evident thata system built to operate according to the principles above set forth inconnection with Fig. 1 will have this second degree of freedom (ortuning) just described at a lower frequency. The entire feeders andthose portions of the individual radiating doublets in the triangularunits falling outside the tapping points on the doublets are theneffective capacities which are tuned by the portion of the radiatingdoublets between the tapping which are effective inductances. This lastmode of oscillation, however, is not preferred, since it calls foragreater ratio of circulating energy in the system to radiated energyfrom the system which tends to give the system a lower power factor andconsequently sharper tuning, a feature not desirable in connection withcommunication on wide frequency band high definition television signals.

It should be notedthat the system of Figs. 1 to 10 hereinabovediscussed, which show a plurality of triangular units stacked inparallel planes, have been energized from the base of the antennastructure. From what has been said before in connection with thesefigures, it Will be apparent that due to the half wavelength or multipleof a half wavelength spacing between the triangular units, the unitswill be excited with voltages of equal magnitude, whether thecharacteristic impedances of the vertical feeders connecting these unitsare matched or unmatched. This is because at half wave intervals alongthe feeders there must appear the same magnitudes of current and voltagesave for an ordinarily unappreciable ohmic loss. A disadvantage of thesearrangements when the stacked triangular units are fed at the base isthe cumulative error of both phase and amplitude along the length of thefeeders which occurs in the presence of sidebands due to the deviationof the sideband wavelengths from the particular wavelength for which thetriangular units are correctly spaced. Thus while the tuningcharacteristic of each triangular unit of the system of Fig. 1 may besufficiently broad to accommodate the sidebands without appreciablechange in ampltude in the radiating elements, the cumulative effectmentioned will disturb, to some extent, the radiation pattern and,therefore, at the distant point of reception cause an apparent greaterchange in received amplitude than that which is actually caused by thetuning characteristic of the triangular units.

The system of Fig. 2, now to be discussed in connection with Fig. 3,shows one preferred embodiment in accordance with the invention and.

overcomes, to a large extent, the foregoing disadvantage by minimizingthe cumulative error just referred to. This is achieved, in brief, by

connecting only the center triangular unit R di-" rectly to the sourceof energy by means of feeder lines and coupling the other triangularunits W and Q, respectively above and below the center unit, to thiscenter unit R. For this p p se there are employed sections of concentrictransmission lines 30 to 35 respectively, whose inner conductors aredirectly connected to the doublets of the center triangular unit andwhose outer conductors serve as coupling feeders for the doublets of thelower triangular unit Q, there being provided an extension 35 of theouter conductor for serving as a coupling feeder for the uppermosttriangular unit W. These self-contained concentric transmission linefeeders provide, among other things, a clean mechanical de sign ofstructure.

Fig. 2 shows three equilateral triangular units Q, R and W in parallelplanes at different levels, spaced one-half wavelength apart, and fed bythree pairs of vertical feeders. In order to more clearly explain themanner in which the doublets of Fig. 2 are fed by and matched to thevertical feeder lines, Fig. 3 shows, in simplified manner, a single pair3|, 32 of the feeders of Fig. 2 with the associated doublets of thedifferent triangular units connected to this pair. Since the other pairsof feeders, namely 33, 34 and 30, 35, are connected in similar manner tothe other doublets of the triangular units, what is set forth hereinafter likewise applies to these other feeders and their associateddoublets.

The middle doublets 31, 31' which are the ones primarily receivingenergy from the inner conductors 38 of the transmission lines 3|, 32 areat their ends 56 connected to feeders 58 running more or less parallelwith the doublets 31, 31'. These feeders 58 connect the ends 56 of thedoublets to the ends 59 of the inner conductors 33 of the concentriclines 3|, 32. These ends 59, as described later, have an impedance whichis rather high, for which reason it is advantageous to make the lastquarter wavelength of the inner conductor 38 of the concentric line havea high er ratio between diameters of inner and outer conductors than therest of the system. As is known, it is the diametrical ratio and not theactual size of the conductors which determines the characteristic orsurge impedance of the line. This quarter wave link of 38 then, by having a load higher than its surge impedance at its upper end 59, willoffer an impedance lower than We now consider two doublets directlyconnected in parallel, close together and connected to each other at theends, we know that they are surrounded by a common radiation field. Inparallel, the doublets form an entity having a 72 ohms resistance at thecenter, as before. causing the field is, however, divided between thetwo conductors of the parallel entity. If, however, the doublets areeffectively in parallel and The current the transmission lines connectedonly to one doublet at its center, the current division is half andhalf, the series resistance at the middle of one of them must then befour times that of a single doublet alone, for the same power. If thedivision of the current between the two doublets effectively in parallelis not equal, the series resistance at the middle of one is equal to 72ohms multiplied by the square of the ratio of the total current in thesystem and that in the branch under consideration. Now, as a matter offact, the inner conductors 38 of the two transmission lines 3|, 32 areconnected to the feeders 58 not at the middle of the system but atpoints farther out (although symmetrical). Due to the falling off of thecurrent towards the ends of a doublet, it can be seen that, on an energybasis, the series resistance of the system is still further increased.The a'ctual length of the feeders 58 between the ends of the doubletsand the ends of the inner conductors 38 of the transmission lines isless than a quarter wave. In the concentric transmission lines,howeventhe center conductor current must have an equal and oppositecounterpart in the interior of the outer conductor, which is called theshell current. This shell current in the outer conductor continuesthrough the aperture in the outer conductor made for the end of thecenter conductor and continues across the mid portion of the system(star connection and center portion of main doublet) to enter in throughthe aperture of the other transmission line to again become the shellcurrent. The star members and the portion of the main doubletintermediate two adjacent transmission lines feeding the same doubletserve to complete the path for the split doublet branch formed by thefeeder. The current from the feeder branch, however, causes a certainvoltage drop across the star members and the middle doublets which isnot obtained in the top and bottom systems. This is equivalent to makingthe inductance of the mid portion of the mid system higher. The lengthof the doublets in the mid system therefore has to be somewhat less thanin the top and bottom systems. The total voltage drop obtained acrossthe mid section (stars and mid portions of the doublets) is, of course,what energizes the top and bottom systems.

In actual practice, due to the shunting effect of the bracing starconnections, the doublets of all the units W, R and Q are very slightlylonger physically than one-half wave, the doublets of the middle unit Rbeing slightly shorter physically than the doublets of units W and Q.Inone embodiment, the upper and lower doublets were about 4% longer thanthe physical length of onehalf wave, whereas the middle doublets wereonly about 2% longer than one-half wave, although it will be understoodthat the electrical length of all the doublets of Q, R and W is aperfect half wave. This difference between the middle doublets and theupper and lower doublets is due to the connections of the feeders 58 tothe ends of the middle doublets.

From the foregoing, it will be appreciated that it is not essential thatfeeders 58 be connected only to the ends 56 of the middle doublets,since they may be tapped to the middledoublets at intermediate pointsdepending upon the impedance matching requirements of the system. Suchimpedance matching requirements, under certain conditions, may even callfor the introduction of lumped reactances in some form in feeders 58.

-For obtaining a 180 phase reversal between the adjacent concentrictransmission lines 34 and 32, there is provided a U-shaped. concentricline section 39 so connected to an energy supply line 40' that there isa path difference between lines 3! and 32 equal to half a wave asmeasured from the point of connection 4!. path to one transmission line32 is half a Wave longer from junction point 4! than to the othertransmission line 3!, and both paths are in parallel relation withrespect to energy line as. Other U-shaped concentric line sections 42and 43 similarly couple the other concentric transmission lines 30, 35and 33, 34 together, and are, in

turn, connected to energy supply feeders 44 and tion. It will thus beseen that the six vertical concentric transmission lines 39 to 35,inclusive, of alternate phase, have been reducedto threeenergy supplyfeeders 48, 44, and 45 of the same phase. To obtain the desiredimpedance matching between the U-shaped line sections 39, 42 and 43 andtheir respective energy supply feeders 4t), 44 and 45, the impedance ofeach feeder 44, 44 and 45 is respectively made to be equal to onehalfthe impedance of the U-shaped line section which it will be observedcomprises two transmission lines in parallel. For example, if theimpedance of each transmission line of the U-shaped section 39 is 48ohms, then the impedance of energy feeder 40 should be 24 ohms for aconnection which is free from reflection. The surge impedance of the Ubranches therefore must be twice that of the T branch feeding into theU. Since the surge impedance of a, line is'equal to \/L/C, L must bedoubled and C divided by two. This gives a factor of 4 under the squareroot, and thus the surge impedance is doubles. It is clear that thisfactor cannot belong to either L or C alone, since L increases as muchas C decreases. L and C are in their turn determined by functions inwhich the variable, the ratio between shell and center conductordiameters, is under a logarithm. That then means that if L is to bedoubled or C out in half, the ratio of diameters must be squared. If Lwas to be made three times and C to be divided by three, the ratio wouldhave to be cubed. It will be seen from this that line dimensions must becarefully chosen in order to avoid impossible mechanical dimensions.

It is now proposed tov connect all three feeders 40, 44 and 45 of 24ohms each toa single feeder. At first blush, one might consider simplyparalleling the three feeders. However, if this is 'done, then for aconnection free from reflection with a single feeder for energizing thethree, there would be required a single feeder whose impedance is equalto that of the three feeders 40, 44 and 45 in parallel, that is, asingle feeder Whose surge im pedance is only 8 ohms. Such a low surgeimpedance is, however, entirely impractical in this case inasmuch as adesirable ratio of four to one between inner and outer conductors of aconcentric line gives a surge impedance of about 80 ohms, and in orderto obtain an impedance of only eight ohms to match the three parallellines 40, 44' and 45 there would be required a ratio between inner andouter conductors of the single feeder of the tenth root of four, anobviously impractical mechanical arrangement because the innera'nd outerconductors would thenhave an extremely small difference in diameter.

In other words, the

The foregoing difficulties are overcomein accordance with the inventionby arranging a circuit whereby the three T feeders 4Q, 44 and 45 areconnected in series and joined to the single feeder 46. By means of thisfeature of the present invention, the impedance required for the singlefeeder 45 is three times that of one of the feeders 40, 44 or 45, inother words 72 ohms. This 'value of impedance is practical and one whichthe mainline or single feeder 48 can be designed to provide. As can beseen, two of the three T branches, 46 and 44, are surrounded by a shell4! which makes the outer conductor of the T branch an intermediate shell48 for the length of a quarter wave. On account of its length, thisintermediate shell 48 has a Very high impedance on its outside. Now,then, the current in the center conductor 49 of the branch 45, which hasno outer shell, becomes the shell current for the middle branch 44 andthe current of the center conductor 50 of the middle branch 44 becomesthe shell current for the branch 4%. The current in 49 cannot go on theoutside of the intermediate sleeve 48 of the middle branch 44 due to thehigh impedance of the quarter wave conductor 4'! but must go on theinside and become the shell current for the middle T branch 44, asalready stated. The shell current of the branch 45, i. e., the currentin the outer conductors, follows the cover 5| and becomes the shellcurrent for the main line 46. The center conductor current of the righthand branch becomes the center conductor current of the main line 46.The three T branches are thus connected in series and in phase with themain line 44. Due to the necessary introduction of cross connectors, 52in this system, it is rather important to make the three T branches 4%],44 and 45 successively longer by an equal amount. Since the voltage ofthe main line 46 is divided by three, a third for each T branch, orsince there are three T branches in series, the surge impedance of eachbranch must be a third of the surge impedance of the main line 45. Theratio of the shell and center conductor diameters of the T branches 4!],44 and 45 must therefore be the cubic root of the ratio in the main line46 as already stated.

Fig. 4 shows an alternative method to that of Figs. 2 and 3 ofconnecting a pair of concentric transmission lines, such as 3|, 32, tothe doublets of three triangular units, and differs from Fig. 3 only inshowing that the concentric lines 3|, 32 may both feed the same doubletin the middle level, instead of different doublets, while feedingdifferent doublets in the upper and lower levels.

Where it is desired to employ two transmitters on the same antennasystem at slightly different frequencies, (A2 and M) as for instance thevideo and audio transmitters for transmitting television programs, afilter system shown in Fig. 5 may be inserted between the main line 46of Fig. 2 and the transmitters proper. This filter system, shown in boxform and designated 53, is described in great detail in United StatesPatent No. 2,128,400, granted August 30, 1938, to which reference isherein made. Obviously the purpose of this filter system is to preventthe energy from one transmitter from entering the circuits of the othertransmitter while permitting both transmitters to freely feed energyinto the antenna system.

Since main feeder 4% is a single concentric line and since thetransmitters in the above mentioned case of Fig. 5 are preferably of thepushpull type, it now becomes necessary to adapt the single concentrictransmission "line system to a push-pull transmission line system forconnecting to the balanced circuit of the transmitter. In this instance,the U-shaped phase transforming arrangement described above inconnection with elements 39, 42 and 43 of Fig. 2 was not found suitablefor providing the proper load impedance required by the push-pulltransmitter. This will be evident from the fact that the main line 46has an impedance of '12 ohms and the total impedance across both legs ofthe U-phase transforming arrangement would have to be 288 ohms, i. e.,each leg of the U would have an impedance of 144 ohms. Such an impedanceof 288 ohms is for most transmitters too high to draw full power. Thisdifficulty is overcome in accordance with another aspect of theinvention which provides a push-pull impedance equal to the impedance ofthe single concentric conductor line which again effects phasetransformation. This circuit comprises a quarter wave concentric line 6|whose inner and outer conductors are each connected at one end 62 to thecenter conductors B3 and 64 of a pair of push-pullconcentrio linebranches. An outer metallic sleeve 66 surrounds the line SI for itsentire quarter wavelength, and is joined to the outer conductors of thepush-pull branches, as shown. To understand the operation of thecircuit, let us visualize the circuit from the transmitter end fromwhich there are fed currents of opposite direction in the two push-pullbranches, as indicated by the arrow marks. Since in a single concentricconductor line the center conductor current and the shell current on theinner surface of the outer conductor are opposite to each other indirection, but of the same magnitude, it follows that the innerconductor of one branch of the push-pull circuit should continue as theinner conductor of the single concentric line 6i while the innerconductor of the other push-pull branch should continue as the shellcurrent of the line 61. To ,prevent short circuiting of the push-pullbranch connected to the outer conductor of line 6|, it is necessary forthe shell of line 6| at point 62 to present a high impedance on itsouter surface, .in which case all current arriving over conductor 64will travel over the inner surface of the shell of line Bl. This isachieved by making sleeve 66 a. quarter wavelength and connecting itsupper end to the outer conductor of line 6|. Since lines 63 and 64 areeffectively in series, each must have a surge impedance equal to halfthe surge impedance of the line 6|; consequently, there will be a surgeimpedance across 63 and 64 of a value equal to the surge impedance ofsingle concentric line 6|. In order not to alter the physicalconfiguration of the system between .filter circuit 53 and the push-pullbranches, one may taper both the inner and outer conductors of thesingle transmission line leading from the .filter to the line 61. Inorder not to change the surge impedance along the tapered section, thediametrical ratio of the conductors in this section should be constant.To preserve neatness of appearance, the metallic sleeve 66is extendedbeyond quarter wave line 61 to form a continuation of the transmissionline leading from filter ,53.

It will be understood, of course, from what has :gone before, that theinvention is not limited to the precise arrangements illustrated anddescribed, since various modifications may be made without departingfrom the spirit and scope of theinvention. 1

What is claimed is:

1. In combination, first and. second concentric feeder lines ofpredetermined impedance, each having inner and outer conductors, a mainconcentric line having an impedance at least equal approximately to thesum of the impedances of said first and second feeder lines, and acircuit for matching the impedance of said main line to said two feederlines and for coupling them together comprising a connection from theinner conductor of said main line to the inner conductor of said firstfeeder line and a connection from the outer conductor of said firstfeeder line to the inner conductor of said second feeder line, quarterWavelength metallic sleeves surrounding the outer conductors of saidfeeder lines from the above mentioned points of connection, and meansfor connecting said sleeve together and to the outer conductor of saidmain line.

2. In combination, first, second and third concentric feeder lines ofpredetermined impedance, each feeder having inner and outer conductors,a main concentric line having an impedance equal approximately to thesum of the impedances of said three feeder lines, and a circuit formatching the impedance of said main line to said feeder lines and forcoupling them together comprising a connection from the inner conductorof said main line to the inner conductor of said first feeder, aconnection from the outer conductor of said first feeder to the innerconductor of said second feeder, a connection from, the outer conductorof said second feeder to the inner conductor of said third feeder,quarter wavelength metallic sleeves surrounding the outer conductors ofsaid first and second feeders from said above mentioned points ofconnection, and means for connecting said sleeves together and to theouter conductor of said main line.

3. A system in accordance with claim 2, characterized in this that saidlast means connects together the quarter Wavelength sleeves at their twoadjacent ends, and also to the outer conductor of said third feeder.

4. A circuit for coupling together a pair of concentric lines adapted tohave opposite instantaneous currents therein with a single con centricline and for matching the impedances between them, comprisingconnections from the inner conductors of said pair of lines to the innerand outer conductors of said concentric line, a metallic sleeve aquarter of a wavelength long surrounding said single line and connectedto the outer conductor of said single line at the end of said sleevewhich is remote from said connections, said sleeve at its other endbeing connected to the outer conductors of said pair.

5. A circuit for efficiently coupling together a push-pull type ofsystem having a pair of conductors with oppositely flowing instantaneouscurrents therein and a concentric feeder line having an inner and anouter conductor, comprising a connection from one conductor of said pairto said inner conductor of said concentric line and a connection fromthe other conductor of said pair to the outer conductor of saidconcentric line, the surge impedance of said concentric line being equalto the sum of the surge impedances of said pair of conductors, and meanssurrounding said concentric feeder line for at least a portion of thelength thereof for preventing the current of the operating frequencyflowing over said last conductor of said pair from flowing over theouter surface of the to the sum of the impedances of said three feederlines, and a circuit for matching the impedance of said main line tosaid feeder lines and for coupling them together comprising a connectionfrom the inner conductor of said main line to the inner conductor ofsaid first feeder, a connection from the outer conductor of. said firstfeeder to the inner conductor of said sec- 1 0nd feeder, a connectionfrom the outer conductor of said second feeder. to the inner condoctorof said third'feeder, quarter wavelength metallicsleeves surrounding theouter conductors of said first and second feeders from said abovementionedpoints of connection, and means for connecting said sleevestogether and to the outer conductors of said main line and. thirdfeeder.

8. The method of coupling a concentric line feeder in series relation toa pair of other C0111- centric feeder lines, each of said concentriclines having an inner and an outer conductor, which comprises connectingthe end of the inner conductor of said first feeder to the end of theinner conductor of one feeder of said pair, connecting the outerconductor of said first feeder to the outer conductor of said one feederof said pair at a predetermined point on said last outer conductorremoved from its end, connecting the outer conductor of said one feederof said pair to'the inner conductor of the'otherfeeder of said pair, andconnecting the outer conductor of said last feeder to the outerconductoro'f said first feeder.

t 9. In combination, first and second concentric, feeder lines ofpredetermined impedance, each having inner and outer conductors, a mainconcentric line having an impedance equal approximately to the sum ofthe impedances of said first and second feeder lines, and a circuit formatching the impedance of said mainline to said two feeder lines and forcoupling them together including a connection from the inner conductorof said main line to the inner conductor of said first feeder line and aconnection from the outer conductor of said first feeder line to theinner conductor of said second feederlline, and a connection from theouter conductor of said second feeder line to the outer conductor ofsaid main line.

10. The method of coupling a plurality of concentric lines, each havinga predetermined-impedance of substantially the same value, to aconcentric. line having an impedance equal SHb'. stantially to the sumof the impedances of said plurality of lines, whichlcomprises couplingall of saidlines together in series relationship, where-. by the innerconductor current of one line of said plurality becomes the outerconductor current of another lineof said plurality.

11. The method of coupling aconcentric line having apredeterminedimpedance to a pair of other concentric lines which are inpush -pull ance substantially equal to half the impedance of said firstline, which comprises connecting the inner conductor of said first lineto the inner conductor of one of said pair, connecting the outerconductor of said first line to the inner conductor of the other of saidpair, connecting the outer conductors. of said pair together and througha connection of predetermined length to the outer conductor of saidfirst line.

12. In a high frequency coupling arrangement, a first circuit comprisinga .pair of concentric lines each having an inner and an outer conductor,the inner conductors of said lines adapted to have oppositeinstantaneous. currents therein, a second circuit comprising a single.concentric line also having an inner and an outer cone ductor, and meanscoupling said circuits to: gether, said means comprising a connectionfrom the inner conductor of the concentric line of said second circuitto the inner conductor of one concentric line of said first circuit, a.connection fromthe outer conductor of the concentric line of said secondcircuit to the inner conductor of the other concentric. line of saidfirst circuit, a sleeve surrounding the outer conductor of said line ofsaid second circuit from a point adjacent the junction points of saidfirst circuit and said second circuit for a distance substantially. anodd multiple of. a quarter of the. operating wave from said junctionpoints, a connection from said sleeve at said distance removed from.said junction pointstolthe outer conductor of said line of said second.circuit, and connections from said outer. conductors of said firstcircuit. to the. endof 1 said sleeveadjacent said junction. points.

13. The method of coupling a pair of concentric lines in seriesrelationship having a predetermined value of impedance across. both of,said lines to a single concentric line.v having a sub.- stantiallyidentical impedance, whichcomprises connecting the end of. the innerconductor of said single line totheend of one inner conductor of sh atfor p venti e u en sof the. pe at n frequency from, flowing over, theouter surface o saidv s a h, s id aux ia y on uc bein concentric withand surrounding said sheath and having a length substantially an oddintegral multiple including unity of a quarter of the wavelength atwhich the system is arranged to 70p,- erate, oneend of said auxiliaryconductor being, open and positioned adjacent, the end ofsaid sheath,the other end being directly connected to the, outer surface of saidsheath,

15. A feeder for electric currents, of highfrequency, said feedercomprising a conductor, a conducting sheath surrounding saidconductor,an auxiliary conductor surrounding said sheath and electricallyconnected thereto, at one end,

theother end of said auxiliary condu tor, being p n p sitioned aiacentthe. end. o aid sheath, said auxiliary, conductor having. suchlength and being. so arranged 1 that itcombines relation, saidotherlineseach having an finned; 7, with a portion of the outer surfaceof;the.-sheath,

measured from the end thereof, of a length substantially the same as thelength of said auxiliary conductor, to form a circuit of high impedanceto the travel of undesired waves along the outer surface of said sheath.

16. In combination, a plurality of concentric, feeder'lines ofpredetermined impedance, each having inner and outer conductors, a mainconcentric line having an impedance equal approximately to the sum ofthe impedances of said plurality of feeder lines, and a circuit formatchingthe impedance of said main line to said plurality of feederlines and for coupling them together comprising a connection from theinner conductor of said main line to the inner conductor of one of saidfeeder lines and a connection from the outer conductor of said onefeeder line to the inner conductor of another of said feeder lines, aquarter wavelength metallic sleeve surrounding the outer conductor ofsaid one feeder line from the above mentioned points of connection, andmeans for connecting said sleeve at one end to the outer conductor ofsaid one feeder line and at its other end to the outer conductor of saidmain line.

17. In combination, first, second and third concentric feeder lines ofpredetermined impedance, each feeder having inner and outer conductors,a main concentric line having an impedance equal to the sum of theimpedances of said three feeder lines, and a circuit for matching theimpedance of said main line to said feeder lines and for coupling themtogether comprising a connection from that end of the inner conductor ofsaid main line nearest said feeders to the adjacent end of the innerconductor of said first feeder, a connection from the adjacent end ofthe outer conductor of said first feeder to the adjacent end of theinner conductor of said second feeder, a connection from the adjacentend of the outer conductor of said second feeder to the adjacent end ofthe inner conductor of said third feeder, metallic sleeves surroundingthe outer conductors of said first and second feeders from said abovementioned ends, and

means for connecting said sleeves together and to the outer conductor ofsaid main line, and at points one-quarter of a wavelengthfrom said endsof the feeder lines which they surround to the outer conductors thereof.

18. In combination, a plurality, including first and second, ofconcentric substantially feeder lines of predetermined impedance, eachhaving inner and outer conductors, a main concentric line having animpedance at least equal approximately to the sum of the impedances ofsaid plurality of feeder lines, and a circuit for matching the impedanceof said main line to said plurality of feeder lines and for couplingthem together comprising a connection from the inner conductor of saidmain line to the inner conductor of said first feeder line and aconnection from the other conductor of said first feeder line to theinner conductor of said second feeder line, means coupling the outerconductor of said second feeder line to the outer conductor of said mainline, metallic sleeves surrounding the outer conductors of said firstand second feeder lines from a point adjacent the junction points ofsaid first and second feeders, and means for connecting said sleeves tothe outer conductors of the feeder lines which they surround at pointsone-quarter of a wavelength from said junction points and for connectingsaid sleeves to the outer conductor of said main line.

19. In combination, a transmission line in the form of a pair ofconductors having opposite instantaneous polarities thereon, a loadconnected across said .pair of conductors at one location, another loadconnected to each of said pair of conductors at another location, saidconductors having one diametrical dimension at said one location and adifferent diametrical dimension at the other location.

20. A feeder system for high frequency electrical currents, comprising aconductor and a conducting sheath surrounding said conductor, a pair ofconductors adapted to have oppositely flowing currents thereover coupledto said first conductor and conducting sheath, and an auxiliaryconductor associated with said sheath for preventing currents of theoperating frequency from flowing over the outer surface of said sheath,said auxiliary conductor being concentric with and surrounding saidsheath and having a length substantially an odd integral multipieincluding unity of a quarter of the wavelength at which the system isarranged to operate, one end of said auxiliary conductor being open andpositioned adjacent the end of said sheath, the other end being directlyconnected to the outer surface of said sheath 21. In combination, asingle transmission line having an outer sheath and an inner conductorand a push-pull pair of balanced transmission lines, a connection fromthe inner conductor of said single line to a conductor of one of saidpush-pull lines, a connection from the sheath of said single line to aconductor of the other of said push-pull lines and an outer shellsurrounding the end portion of said single line, said shell beingconnected to said sheath at a distance equal to the quarter of thelength of the operating wave from the end of said single line.

22. Means for coupling a single concentric line having an outer sheathand an inner conductor to a push-pull pair of concentric transmissionlines each having an outer sheath and an inner conductor comprising aconnectionfrom the inner conductor of said single line to an innerconductor of one of said pair of lines, a connection from the end of thesheath of said single line to the inner conductor of the other of saidpair of lines, an outer shell surrounding the end of said single linesand its junction with said pair of lines, said shell being connected tothe outer sheath of said single line at a distance equal to a quarter ofthe length of the operating wave from the end of said sheath.

23. Means for coupling a single concentric line having an outer sheathand an inner conductor to a push-pull circuit having a pair ofconductors adapted to be energized in an opposing phase relationshipcomprising a connection from said inner conductor to one of said pair ofconductors, a connection from the end of said outer sheath to the otherof said pair of conductors and an outer shell surrounding the end ofsaid single line and its junction with said pair of lines, said shellbeing connected to said outer sheath at a distance equal to a quarter ofthe length of the operating wave from the end of said sheath.

24. Means for coupling a single concentric line having an outer sheathand an inner conductor to a push-pull circuit having a pair ofconductors adapted to be energized in an opposing phase relationshipcomprising a connection from said inner conductor to one of said pair ofconductors, a connection from the end of said outer sheath to the otherof said pair of "conductors and an outer shell surrounding the end ofsaid single line, said shell being connected to said outer shell at adistance equal to .a quarter of the length of the operating wave fromthe end of said sheath.

'25. In combination, a concentric line having an inner conductor and anouter conductor, a source of high frequency energy coupled to said lineand means for presenting at a predetermined point on the outer surfaceof said outer conductor a high impedance to the energy of said sourcecomprising an auxiliary conducting. sleeve surrounding said outerconductor, a connection between said sleeve and said outer conductor,the distance between said predetermined point and said connection beingan odd multiple,including unity, of a quarter of the wavelength of saidenergy.

26. In combination, a concentric line having an inner conductor and anouter conductor, high frequency apparatus coupled to said line and meansfor presenting at a predetermined point on the outer surface of saidouter conductor a high impedance to the operating frequency of said highfrequency apparatus comprising an auxiliary conducting sleevesurrounding said outer conductor, a connection between said sleeve andsaid outer conductor, said sleeve surrounding said outer conductor foran effective electrical distance corresponding to an odd multiple,including unity, of one quarter of the wavelength of the operatingfrequency of said apparatus from the point of connection between saidsleeve and said outer conductor to said predetermined point.

NILS E. LINDENBLAD.

